In shell and tube heat exchangers, such as nuclear steam generators, tube supports are used to minimize tube vibration induced by the fluid flowing on the shell side of the exchanger. These tube supports may be drilled plates, machined plates with various clearances around the tube or lattice supports built from metal strips or bars. In any event, there exists areas of tight clearance between the tube and support which can be referred to as crevices. In many cases, the shell side fluid, which is the fluid being heated, in flowing through the crevices is partially or wholly evaporated by the heat transferred from the tube side fluid to the shell side fluid. One consequence of the evaporation process is that the concentration of dissolved solids in the liquid phase may reach the saturation limit so that further evaporation of water will result in precipitation of solids on the tube or plate surfaces. The crevice formed by a tube and the support is especially vulnerable to high solids deposition due to part or total evaporation of the water as it flows through the crevice. The solids accumulation in the crevice is undesirable, as it can lead to complete blockage of flow through the crevice, which increases shell side pressure drop, and may induce localized tube corrosion or other phenomena which could reduce the service life of such tube.